Perimeter weighting in a golf club distributes the mass of the club toward the perimeter, minimizing the effects of off-center hits on the face of the golf club away from the sweet spot and producing more accurate and consistent golf ball trajectories. Perimeter weighting is achieved by creating a cavity in the back of the golf club opposite the face or hitting surface. The material weight saved by creating this cavity is redistributed around the perimeter of the golf club head. In general, larger cavity volumes correspond to increased amounts of mass distributed around the perimeter. Additionally, more of the perimeter weight is moved to the sole of the club to move the center of gravity downward and rearward.
Alternative approaches for moving the center of gravity of a golf club head rearward and downward in the club head utilize composite structures. These composite structures utilize two, three, or more materials that have different physical properties including different densities. By positioning materials that provide the desired strength characteristics with less weight near the crown or top line of a golf club head, a larger percentage of the overall weight of the golf club head is shifted towards the sole of the club head. This results in the center of gravity being moved downward and rearward. This approach is advantageously applicable to muscle back iron clubs or fairway woods, as this will help to generate loft and power behind and below the ball.
Additionally, to improve ball speed and distance in club head design, particularly in the construction of irons, designers and manufacturers may opt to use a cup face structure. A thin cup face and return combination results in an increase in flexing of the face and sole, which, in turn, results in a decrease in the deformation of the ball upon impact and an overall decrease in the loss of energy in the collision. The reduced energy loss is due to the fact that metals generally exhibit more elastic behavior in a collision than viscoelastic materials such as rubber, urethanes, and other polymers that are typically used to make golf balls. To further enhance performance, current iron club head designs take advantage of certain materials for the ball-striking face, such as titanium, that provide higher compliance (i.e., relatively low modulus) than other metal materials and are relatively lightweight when compared to typical club head metals, such as steel.
However, there are limitations when using multiple materials for the construction of a club head, as club head designs may often be constrained by the manufacturing requirements associated with using multiple materials. For example, weld lines, swage geometry, adhesive bonding ledges, and the like, all must be taken into account. Manufacturers must be able to join two dissimilar materials with sufficient strength, which can be particularly difficult depending on the materials being joined to one another. For example, some materials must be bonded together by welding, swaging, or using bonding agents such as epoxy. However, such bonds may be subject to delamination or corrosion over time, and may further limit the potential of the materials and restrict performance. For example, current methods for creating a cup-faced iron club head from titanium generally involve brazing a titanium cup to a steel body, wherein the swage joint or glue joint is required to be built up with body material to attain a correct bonding surface and/or joint durability. However, such a manufacturing method generally requires a lip for encasing the titanium cup to the body, which can have a negative impact on performance of the cup face, such as restricting the club head's ability to flex and take advantage of the combination of high strength and low modulus that titanium possesses.
Therefore, there remains a need for a composite golf club head that utilizes components having different materials and/or densities designed in such a way as to minimize the problems associated with delamination, corrosion, or separation of the components while further maximizing the performance potential of each component.